Department of Medical Physics, Royal Perth Hospital, Western Australia,
Valendar F Turner, John Papadimitriou, Barry Page, David, Causer, Helman Alfonso
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It is the role of the doctor, not the patient, to interpret tests
Foley quotes the Perth Group: "Do patients really play a role in
interpreting their own tests?"
responds “And my answer is that of course they do in most cases, and they
always should. The patient always
knows more about the patient's history than the doctor does. An accurate diagnosis depends on more than test results, it
also requires putting those results into the context of the whole
picture…likewise for HIV antibody testing, the person being tested knows more
about their history of sexual activities, IV drug use and needle sharing, and
is no doubt the patient does know more about his medical history than his
doctor. The doctor’s skill lies in
obtaining that history and formulating it in such a manner he can decide whether
or not a test is likely to assist arriving at a diagnosis.
On many occasions no test is warranted.
The greatest physician who ever lived, Sir William Osler, taught his
“Talk to the patient long enough and he will tell you what is wrong
with him”. However, once a test
is performed the patient plays no role in interpretation.
Not even if the patient is a doctor.
A visit to the coronary care unit of any hospital will not reveal
patients sitting up in bed studying their chest X-rays or ECGs.
Foley appears to believe particular antibody test results (using criteria of his
choosing), indicates HIV infection if the person being tested has a history of
“sexual activities, IV drug use and needle sharing, and transfusions”.
What Brian avoids is telling us how he interprets the same test result in
a person who is not in a risk group and is healthy.
positive test in a healthy, no risk person does not indicate HIV infection then
how does Brian reconcile this with the advice from the CDC that “HIV testing
consists of an initial screening with two types of tests commonly used to detect
HIV infection. The most commonly used initial test is an enzyme immune assay (EIA)
or the enzyme-linked immunosorbent assay (ELISA).
If EIA test results show a reaction, the test is repeated on the same
blood sample. If the sample is repeatedly the same result or either duplicate
test is reactive, the results are "confirmed" using a second test
such as the Western blot. This
more specific (and more expensive) test can tell the difference between HIV
antibodies and other antibodies that can react to the EIA and cause false
positive results. False positive EIA results are uncommon, but can occur.
A person is considered infected following a repeatedly reactive result
from the EIA, confirmed by the Western blot test” (emphasis added).
CDC assertion makes no mention of the patient’s history, healthy or otherwise. For the CDC, as for all HIV experts, the tests are considered
virtually 100% specific rendering clinical data irrelevant.
we read: In 1999 “Of the estimated 800,000--900,000 persons infected in the
United States, approximately one third have yet to be diagnosed”. At www.cdc.gov/mmwr/preview/mmwrhtml/mm5225a1.htm
the CDC report: “In 2000, an
estimated 850,000--950,000 persons in the United States were living with HIV,
and approximately one fourth of these persons did not know they were infected
In reference 1 (www.cdc.gov/mmwr/preview/mmwrhtml/mm4923a2.htm),
“During January 1997--September 1998, 615 persons with HIV infection diagnosed
and reported met the criteria for the study; these persons represented 15% of
all persons with HIV infection diagnosed and reported during this period from
Alabama, New Jersey, and Tennessee. Of
the 543 persons determined eligible after follow-up by state health departments,
180 (33%) completed interviews, 127 (23%) refused to be interviewed, and 235
(43%) could not be located. Among persons with known dates, 148 (86%) of 173 were
interviewed within 12 months of the self-reported date they learned they were
HIV-infected (median: 6 months)”.
(28%) of 81 males and 69 (70%) of 99 females could not be classified as having
recognised transmission risk or as having sexual contact with an HIV-infected
partner or one with a documented transmission risk…Among 68 males stating a
primary reason for being tested, the leading reasons were because a doctor or
friend told them to be tested (28%) and because they were worried they might be
infected even though they were not sick (22%). Among 90 females stating a
primary reason for testing, the leading reasons were because of pregnancy care
(33%) and because a doctor or friend told them to be tested (18%)…Of 180
persons interviewed, 151 (84%) reported receiving medical care for HIV infection
since diagnosis. Among the 27
persons who responded that they had not received medical care for their HIV
infection since diagnosis, 13 (48%) reported feeling well and not thinking it
was important to seek medical care right away, and 12 (44%) reported not wanting
to think about being HIV-positive as reasons for postponing seeking health care
Clearly, in this study there are a number of seropositive, healthy people devoid of risk factors. (We could also argue “could not be classified…” is CDCspeak for “has not admitted risk factors to the study authors”). This raises a number of questions:
Brian also doubts that in the MultiCenter AIDS Cohort
Studies a single “strong” Western
blot band was considered “proof” of HIV infection.
He also states “A single band may have been all that was required for
enrollment in the study, but scientists rarely speak of “proof” of
Lastly, Brian would like to know how many men in the MACS had one “strong” band. So would the Perth Group, especially given (3). Unfortunately, the individual Western blot patterns are not published. Brian’s “understanding” is that “almost all HIV-infected people produce strong immunological responses to many HIV proteins during the course of their infection, and almost none (perhaps less than 2%?) produce an immunoglobulin response to only one of the HIV-1 proteins”. Brian may be right but upon what data is his “understanding” based? The fact is that once a laboratory or institution or country sets its criteria for a positive Western blot then any patterns not fulfilling these criteria are either negative or indeterminate. According to HIV expert Anthony Fauci, “There are two possible explanations for an indeterminate western blot result. The most likely explanation is that the patient has antibodies that cross react with one of the proteins of HIV…the least likely explanation…is that the individual is infected with HIV” (Harrison’s Principles of Internal Medicine, 13th edition, page 1584). It is also an inescapable fact that the positive criteria under one laboratory, institution or country may be indeterminate under another. In this regard, Brian’s explanations about changing band patterns during the early days of an individuals' infection or percentages of seropositives who do not have “strong immunological responses” are irrelevant. If Brian believes that sooner or later all WB band patterns “evolve” into a particular pattern he asserts diagnostic of HIV infection, (a) what pattern is it? (b) what is his proof; (c) why isn’t this pattern universal?
Would anyone entertain the ECG criteria for an acute myocardial infarction differing between countries? Or the radiological criteria for an acute, traumatic dissection of the thoracic aorta? Could the same patient have an AMI or aortic rupture in one country but not in another? Can Brian Foley, or anyone else, please explain how the diagnosis of infection with the same virus using the same antibody test can be based on ten or more different sets of criteria?
Competing interests: None declared